Many devices are known for transferring linear motion to rotary motion. For example, the linkage in an internal combustion engine between the pistons and the crankshaft transfers the linear reciprocating motion of the pistons to the rotary motion of the crankshaft. Some mechanisms that transfer linear to rotary motion, such as in the example of the linkage in the engine, are dedicated to continuous motion. Other mechanisms, instead of providing continuous motion, constrain the motion between limits of travel. Some push-pull or toggle mechanisms are examples of such mechanisms. However, the known mechanisms lack the ability to geometrically lock at the limits of travel.